Various analyzing devices, such as, for example, medical devices, use various types of connectors that are used as mediators for connecting between the medical device interface (the instruments itself) and external constituents, such as tubes, cannules, and the like that may be of the disposable type. An example of such medical device is a capnograph, which is an instrument for analyzing exhaled breath. A capnograph samples air that is exhaled by a subject by using a small tube, also known as sample line. One end of the sample line may be connected to an air passageway of a respirator or to a cannula attached to, for example, the subject nostril. The other end of the sampling line is connected, through a connector to the instrument itself. The sampling line, including the tube, the connector and other constituents, such as filters, and the like is, in most cases disposable and is replaced for each patient and for each patient type. For example, a subject which is a child will have a sampling line which is different (for example, in size) than a sampling line of an adult subject.
In general, the shape of a connector is standardized throughout the industry, such that tube assemblies of various manufacturers may be interchangeably used with any analyzing instrument. Hence, the manufacturer of a particular type of analyzing instrument has generally no control over which type of tube is used with his instrument. Therefore, to ensure optimal functioning of the instrument, and for commercial reasons, the manufacturer of an analyzing instrument may want to exert such control. In particular, he may want to stipulate that only a certain class, type and/or model of tube assemblies be connected to, and used with, his instrument. Such a class may, for example, consist of tube assemblies that include a specific constituent, such as, for example, a filter, or such that are manufactured directly by him or to his specifications or under his supervision or license.
Enforcing such stipulation may be performed by various means, such as, for example, by using a unique interlocking key arrangement between the connector and the instrument; having a system by which the correct tube assembly would be identified as such by the instrument, whereupon its operation would be enabled, and to disable the instrument otherwise, such as for example, by using electro-mechanical fitting, electrical fitting, and the like. Benefits of such arrangement would be that the instrument would be prevented from operation also when no tube is connected at all or when even a correct tube is improperly connected, thus avoiding damage to sensitive parts of the instrument and also causing incorrect readings. Yet another purpose may be served by such a system, namely identifying the tube assembly as belonging to one of a number of classes and informing the instrument of the particular identity detected, so as to enable it to automatically operate differently for the different classes.
There is thus a widely recognized need for, and it would be highly advantageous to have, a fluid analysis system that includes the capability of determining that a tube assembly has been properly connected to the analyzing instrument and that the tube is of a certain class. Such a capability should be compatible with the standard shape of connectors being used, as well as with the medical environment, and should be reliable and inexpensive.